Optical objective



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OPTICAL OBJECTIVE T2, o 3 I Original Filed Dec. 15, 1941 X Z o #5,

R5 R6 Ra R9 +6427 o -5066 +7420 +3746 HG2 R4 R/o R/ R2 +23/2 +/2s7 +6@ +8@ R3 "m 'H44 3g:

" o/ s/ o2 Y H '/39/ S2 m D4L -ool 2432-0137 4619 F/G.3.

R3 R4 R5 e R7 W +3505 25-ao f/o2 +2955 R2 Ra +7262 +5238 Rl R9 Hose l42e 0/ s/ o2 0.?@04 sa o5 -loa/ -0094 -2453 fn '/00/ -ls m7 vos:

[+2 Inventors AJv/mz/An Patented Dec. 31, 1946 UNITED STATES PATENT OFFICE OPTICAL OBJECTIVE Original application December 15, 1941, Serial No.

423,118. Divided and this application April 24, l

1943, Serial No. 484,425. In Great Britain December 2, 1940 13 Claims.

1 This application is divisional from application Serial No. 423,118, led December 15, 1941, and which has become United States Patent No. 2,319,171, dated May 11, 1943.

The invention of such prior application relates 5 to optical objectives for photographic or like vergent elements is made of a glass having an purposes, comprising two or more divergent ele- Abb V number less than 50. ments and two or more convergent elements, and The present invention has for its Primary 0b' corrected for spherical and chromatic aberraject to extend the application of the invention tions, coma, astigmatism, curvature of field and of such prior application to other types of objecdistortion, and having small zonal spherical tives. aberration, and has for its object to provide A more particular object is to apply the ingood correction for secondary spectrum without vention to an objective of the kind having two sacricing correction for astigmatism iield curvdivergent elements compounded together. ature and distortion. Another detailed object is to apply the said in- This object is achieved according to the invenvention to known types of objective having at tion of the prior application by employing an allea-st one divergent element, by so modifying the kaline halide crystal for one of its divergent eleobjective as to provide two divergent elements ments and optical glass for the remaining elecompOunded together in place of the said single ments, the objective approximately fulfilling the divergent elementtwo equations Further objects of the invention will be apa 1 z parent from the appended claims and from the 2 .:0 and Efbnl=0 following description of the accompanying drawf" VP f1 Vf' ing, in which wherein mp, fp, Vp and 9p respectively represent 25 toltnlllgeuivnstlivs a' telephoto objectlve according 2 a element p of the objective and the symbol z inmventon of a known type of oblective having five simple components of which the first and dicates algebraical summation of the expressions f rth divergent a d th th th for all the elements of the objective. It should Vgentald n e o er ree con' Fexcetglerahg tggrq'l Itlrig Figure 3 shows a modification according to the ratio hp/hi, where hp and h1 are respectively the rnli lgf anlngrittyl ofhiletvetllilainig ordinates of the point of intersection with the lens divergentpan thi Othe thrg cmvergentlr s element p and with the first lens element of a of of through the conjugate points for which the obr t th d.. g f 2 W l 2 jective is corrected, and also that Vp and 0p have Vp een e rfa n o curya ure of the indi' their usual significance, namely ldua teils s1. aes-cmintmg from the front 40 the positive sign indicating that the surface is D l I ne convex to the front and the negative sign that PM C and 0p=m it is concave thereto, D1, Da

axial thicknesses of the individual lens elements, Where no, no, ne, nF and ng are respectively the and S1, S2 refractive indices of the element p for the lines the ail' gaps betWeen the COmDOIlentS. The tables C, D, e, F and g. The prior application describes also give the mean refractive indices nn, the and claims more especially the application of Abb V numbers, and the relative partial disthis invention to objectives of the kind having persions for the intervals (e to g) (C to F) of two compound divergent components located bethe glasses or crystals used for the individual tween two simple convergent components and elements.

2 each comprising a divergent element compounded with a convergent element. In such objectives, preferably, one divergent element is made of an alkaline halide crystal and the other of dense flint glass and at least one of the conrepresent the represent the axial lengths of The example shown in Figure 1 is of the type known as a telephoto objective wherein known examples using glass throughout have suffered from serious* secondary spectrum. Such objectives usually consist of a pair of meni'scus doublets with their concave surfaces facing one another, but in the present example the front component consists of a divergent element cemented between a front convergent element and a rear divergent element, the rear component consisting of a divergent element cemented in front of a convergent element.

Example I Equivalei'fofca length Relative aperture F/5.6

Relative T111 k R f t1 Abb V dlgarthl c ness or e rec ve rs on Radius separation index n.. number e g .D1 0423 l. 5732 51. 9 1. 012 R2. 5768 .DI 0115 1. 6634 21. 3 987 Rrl. 390

D3 0115 1. 052 33. 5 l. 07 R4+. 5585 This example uses potassium iodide crystal for the divergent middle element of the front component and dense flint glass for the divergent rear element of the front component as also for the convergent rear element of the rear component, the front elements of the rst and second components being respectively made of light barium int and crown glasses.

This example may be modied by employing the crystal for the rear element of the front component and the dense flint glass for the middle element, or again by making the rear component of triplet construction and the front component of doublet construction with the crystal as one of the elements, preferably the middle element, of the rear component.

According to a further feature of the invention an objective of known type having at least one divergent element and two or more convergent elements is modified to aord correction for secondary spectrum by replacing the divergent element (or one of the divergent elements) by two divergent elements compounded together, one of such elements being made of an alkaline halide crystal, whilst the other and also the remaining elements of the objective are made of optical glass. The divergent element compounded with the crystal element is preferably made of dense int glass.

Examples II and III of which data are given below, are two such arrangements, (whose analogues form the subject respectively of the present applicants copending United States patent applications Serial Nos. 364,453 and 401,648, now Patents No. 2,298,853 dated October 13, 1942, and 2,310,502 dated February 9, 1943, respectively) and retain the advantages of such prior objectives with the added advantage in each case of greatly improved correction for secondary spectrum.

Example II Equivalerlltol length Relative aperture F/lA Relettiglle par Radius 21913: Refractive Abb v dispersion separation index n.. number a D1 1013 1. 516 64. l 0. 988 Rz-H. 267

Si 1.395 Ra-H. 447 RH- 031 D: 1391 1. 6125 37. 3 1. 051

s. .0101 R5+. 6427 R D: .2432 1.6125 59.6 .999

D4 1619 l. 6973 30. 5 1. 067 Rei-1.420

f Ds 1721 l. 6634 21. 4 988 129+. 3746 S4 .2343 R10-l'. 8120 De 1391 1. 6216 60. 2 998 R11-1. 280

Example III In the second example the objective comprises five components of which the rst and fourth are divergent and the others convergent, the fourth component being compound and consisting of two divergent elements, whilst the remaining four components all consist of simple elements. Potassium iodide crystal is used for the rear element of the fourth component and dense flint glass for the front element thereof. Dense flint glass is also used for the convergent second component, the other two convergent components being made of dense barium crown glass, whilst barium silicate crown glass is used for the divergent front component.

In the third example the objective comprises a divergent compound component located behind two simple convergent components and in front of a third simple convergent component, the front and rear divergent elements of the divergent third component being made -respectivelyv of dense flint glass and'of potassium iodidecrystal. The convergent front component is made-of dense barium crown glass, and the convergent second component of light barium flint glass, whilst dense int glass is used for the convergent rear component.

Search Rooi It will be appreciated that the foregoing examples may be modified in various ways within the scope of the invention, for instance by the use of other high index alkaline halide crystals in place of the potassium iodide crystal described.

What we claim as our invention and desire to secure by Letters Patent is:

1. An optical objective, corrected for spherical and chromatic aberrations, coma, astigmatism, eld curvature and distortion, and having small zonal spherical aberration, and comprising at least two divergent elements and at least two convergent elements in axial alignment, one of the divergent elements being made of an alkaline halide crystal and being compounded with a divergent element made of a dense flint glass, whilst at least one of the convergent elements is made of a glass having an Abb V number less than 50, the remaining elements of the objective all being made of optical glass, the objective approximately fulfilling the two equations m 1 aia: f1J V. 0 and Z"t, V.. o wherein mp, fp, Vp and 0p respectively represent the magnification, the focal length, the Abb V number and the relative partial dispersion of an element p of the objective and the symbol E indicates algebraical summation oi the expressions for all the elements of the objective.

2. An optical objective corrected for spherical and chromatic aberrations, coma, astigmatism, field curvature and distortion and having small zonal spherical aberration, and comprising two compound meniscus components with their airexposed concave surfaces facing one another, one of the components consisting of two divergent elements and one convergent element and having one of its divergent elements made of an alkaline halide crystal, whilst all the other elements of the objective are made of optical glass, the objective approximately fulfilling the two equations wherein mp, fp, Vp and 0p respectively represent the magnification, the focal length, the Abb V number and the relative partial dispersion of an element p of the objective and the symbol E indicates algebraical summation of the expressions for all the elements of the objective.

3. An optical objective as claimed in claim 2, in which the front component is of triplet construction including the crystal element and the rear component consists of a doublet.

4. An optical objective as claimed in claim 2, in which the crystal used has a mean refractive index greater than 1.64.

5. An optical objective as claimed in claim 2, in which the crystal is used for the middle element of the triplet component.

6. An optical objective as claimed in claim 2, in which the front component is of triplet construction and has its middle element made of an alkaline halide crystal having mean refractive index greater than 1.64, and the rear component consists of a doublet.

'7. An optical objective as claimed in claim 2, in which the front component is of triplet construction having its middle element made of potassium iodide crystal and the rear component consists of a doublet, the rear elements of the two components each being made of dense flint glass, whilst light barium flint and crown glasses are used respectively for the front; elements of the front and rear components.

8. An optical objective as claimed in claim 1, in which the two divergent elements compounded together are disposed behind two simple convergent components and in front of another simple convergent component.

9. An optical objective corrected for spherical and chromatic aberrations, coma, astigmatism, field curvature and distortion and having small zonal spherical aberration, and comprising four components in axial alignment, of which the front two components and the rear component each consist of a simple convergent element and the third component is an asymmetrical divergent component consisting of two divergent elements compounded together, in which the objective approximately fulfils the two equations wherein mp, fp, Vp and 0p respectively represent the magnification, the focal length, the Abb V number and the relative partial dispersion of an element p of the objective and the symbol E indicates algebraical summation of the expressions for all the elements of the objective.

10. An optical objective corrected for spherical and chromatic aberrations, coma, astigmatism, eld curvature and distortion and having small zonal spherical aberration, and comprising five components in axial alignment, of which the first and fourth are divergent and the other three convergent, the fourth component rconsisting of two divergent elements compounded together whilst the other four components each consistof a simple element, in which the objective approximately fulfils the two equations mgl: 3.91: Z .Vp 0 d 212V.

wherein mp, fp, Vp and 0p respectively represent the magnification, the focal length, the Abb V number and the relative partial dispersion of an element p of the objective and the symbol E lndicates algebraical summation of the expressions for all the elements of the objective.

11. An optical objective having numerical data substantially as set forth in the following table:

Eqmvalerlmcal length Relative aperture F/lA Rertatiive p a Radius Tless Refractive Abb V dispersion separation index n number e g RPI-2. 312

.Di 1013 1. 516 64. 1 988 RPI-1. 267

Si 1. 395 Bri-1. 447

DI 1391 1. 6125 37. 3 1. 051 RPI-6. 031

Si 0101 R5+ 6427 .DI 2432 1. 6125 59. 999 Ra D4 1619 1. 6973 30. 5 L 057 RS4-1. 420

D5 1721 l. 6634 21. 4 988 Rn+ .3746

Si 2343 Rl0+ .8120

DI! 1391 1. 6216 60. 2 998 R11-1. 286

wherein R1, R2 indicate the radii of the individual surfaces counting from the front, D1, D: indicate the axial thicknesses of the individual elements and S1, S2 indicate the axial air separations between the components.

12. An optical objective having numerical data substantially as set forth in the following table:

Equivalerllggca] length Relative aperture FllA Relattiie ar e Radius Tlgfgess Refractive Abb V d persiou separation index n number 6 0 Rx-H. 066

Dl 1081 1. 0135 59. 6 0. 999 RTI-7. 262

D; 2453 l. 5732 51. 9 1. 012 R4+3 505 Sz 1747 R' 5238 1081 1 613 a7 3 1 051 D; Rl-L 428 wherein R1, R2 indicate the radii of the individual surfaces counting from the front, D1, D2 indicate the axial thicknesses of the individual elements and S1, S2 indicate the axial air separations between the components.

13. An optical objective having numerical data substantially as set forth in the following table:

Equivale lllffw length Relative aperture F/5.6

Relative Thi kn R l ti Abb V difmkl c ess or e rac ve s s on Radius separation index 111 number erg .Dz .0115 1. 6634 21.3 .987 liv-1.390

D1 .0082 l. 509 64.3 .994 R-. 6702 Ds .0170 1.613 36.9 1.051 R7. 2152 wherein R1, Ra indicate the radii of the individual surfaces counting from the front, D1, Dz indicate the axial thicknesses of the individual elements and S1 indicates the axial air separation between the components.

ARTHUR WARMISHAM. CHARLES GORRIE WYNNE. 

